Air-fuel mixture control system

Abstract

Method and means are provided for effecting the controlled vaporization of a liquid fuel to simplify the ability to control a specific air-fuel ratio for an internal combustion engine. The invention contemplates two basic operations: first, a vaporized fuel is provided in which the fuel content is precisely known. This is accomplished by vaporizing liquid fuel with a diluent gas and separating out any fuel droplets so that the vaporized fuel is provided at the dew point. Second, orifice-venturi combination meters are incorporated in the inlet air and fuel flow paths providing respective air and fuel pressure signals which, when balanced against each other, establish a desired air-fuel ratio over a desired operating range of the internal combustion engine.

What is claimed is: 
     
       1. A method of vaporizing fuel and maintaining a desired ratio of air to fuel mixture in an internal combustion engine including the steps of: a. holding the temperature of a liquid fuel and a diluent gas substantially constant prior to mixing:   b. mixing said diluent gas with said liquid fuel such that an excess of fuel is provided to super saturate the gas with fuel;   c. separating out fuel droplets from the super saturated gas by passing the mixture of diluent gas and liquid fuel through a change of momentum separator to provide gas saturated with vaporized fuel resulting in fuel vapor at the dew point;   d. passing the fuel vapor at dew point along a direction to mix with incoming air;   e. generating an air signal constituting a function of the air flow per unit time;   f. generating a fuel signal constituting a function of the fuel flow per unit time while in the vaporized state; and   g. controlling the fuel flow per unit time along said direction in accordance with a given relationship between the generated signals to thereby maintain a desired ratio of air-to-fuel mixture in said internal combustion engine.   
     
     
       2. The method of claim 1, in which said diluent gas is taken from the exhaust of said internal combustion engine. 
     
     
       3. The method of claim 1, in which said generated signals are pressure signals provided by: a. passing the incoming air flow through a venturi-orifice meter combination to result in air pressure variations with variations in the air flow per unit time;   b. passing the fuel through a venturi-orifice meter combination to result in fuel pressure variations with variations in the fuel flow per unit time; and   c. balancing the air pressure signal against the fuel pressure signal when a desired air-to-fuel flow is established.   
     
     
       4. A fuel vaporizer and control system comprising, in combination: a. a pipe section arranged to be inserted between the air intake and input manifold of an internal combustion engine, said pipe section including an air inlet valve means for controlling inlet air flow and a fuel vapor inlet, said air inlet valve means including an orifice-venturi meter combination providing an air pressure signal in accordance with the setting of the inlet valve means;   b. a vaporizer unit including a closed chamber having a liquid fuel inlet connected to receive liquid fuel for said engine, an exhaust gas inlet connected to receive exhaust gases from said engine, and a fuel vapor outlet;   c. a liquid fuel reservoir in said chamber,   d. level responsive means within said chamber to maintain the level of liquid fuel in said chamber at a given level;   e. exhaust pipe connecting means passing from said exhaust gas inlet through a portion of said chamber and thence extending into said liquid fuel to terminate beneath the surface of said liquid fuel, the terminal end of said connecting means beneath said liquid level including outlet means so that exhaust gases can only escape into said chamber by bubbling up through said liquid fuel;   f. separating means in said chamber, said fuel vapor outlet passing from said chamber at a point following the separating means and connecting into said fuel vapor inlet in said pipe section;   g. a fuel valve for controlling the flow of vaporized fuel into said fuel vapor inlet, said fuel valve including an orifice-venturi meter combination providing a fuel pressure signal in accordance with the setting of said fuel valve, the areas of the respective orifices in the air inlet valve orifice-venturi meter and fuel valve orifice-venturi meter being sized such as to equalize said air pressure signal and fuel pressure signal when a desired air-to-fuel ratio is established; and,   h. control means conected to said air inlet valve means and fuel valve responsive to the relative flows of air and fuel respectively therethrough to maintain a desired ratio of air to fuel whereby hot exhaust gases pass through the exhaust pipe connecting means and bubble through the liquid fuel to vaporize the same, the vaporized fuel passing through the separating means to thereby remove any liquid droplets not vaporized so that substantially only vaporized fuel at dew point passes through said fuel valve into said fuel inlet in said pipe section to then mix with air passing through said air inlet valve means and provide an explosive air and fuel mixture at said desired ratio for said engine, said control means including a pressure differential responsive means receiving said air pressure signal and fuel pressure signal connected to said fuel valve to automatically change the setting of said fuel valve whenever a pressure differential exists between said air pressure signal and said fuel pressure signal to change the flow rate of fuel in a direction to equalize said air pressure signal and fuel pressure signal whereby the established air-to-fuel ratio is maintained over a desired operating range of said internal combustion engine.   
     
     
       5. A system according to claim 4, in which said exhaust inlet to said vaporizer includes a check valve to block reverse flow of gases from said chamber. 
     
     
       6. The subject matter of claim 4, in which said pressure differential responsive means includes a cylinder having a double acting piston connected to said fuel valve for changing the setting of said fuel valve in one direction or the other in response to movement of said piston in said cylinder in one direction or the other; and an amplifier means including a slide valve having an inlet and first and second outlets, said inlet being connected to a source of vacuum and said outlets being connected respectively to opposite ends of said cylinder, movement of said slide valve from a center position increasing the vacuum applied to one outlet and decreasing the vacuum applied to the other outlet, said amplifier further including pressure responsive diaphragm means positioned to engage said slide valve and having inlet passages on opposite sides connected respectively to receive said air pressure signal and fuel pressure signal whereby movement of the slide valve as a result of a differential pressure across said diaphragm means applies an amplified differential pressure across said double acting piston in said cylinder. 
     
     
       7. The subject matter of claim 6, including a vacuum accumulating chamber connected between the manifold of said internal combustion engine and the inlet of said slide valve to provide said source of vacuum. 
     
     
       8. The subject matter of claim 6, in which small bleeder holes are provided in the connection between said outlet and opposite ends of said cylinder for said double acting piston to permit the proper fuel valve position to be maintained by said double acting piston under rapid pressure changes during rapid changes in inlet air flow. 
     
     
       9. An air-fuel mixture control system for an internal combustion engine including, in combination, an air inlet valve means for controlling inlet air flow per unit time and including an orifice-venturi meter combination providing an air pressure signal in accordance with the setting of the air inlet valve means; a fuel valve for controlling fuel flow per unit time and including an orifice-venturi meter combination providing a fuel pressure signal in accordance with the setting of said fuel valve, the areas of the respective orifices in the air inlet valve orifice-venturi meter and fuel valve orifice-venturi meter being sized such as to equalize said air pressure signal and fuel pressure signal when a desired air-to-fuel ratio is established; differential responsive means receiving said air pressure signal and fuel pressure signal connected to said fuel valve to automatically change the setting of said fuel valve whenever a pressure differential exists between said air pressure signal and fuel pressure signal to change the flow rate of fuel in a direction to equalize said air pressure signal and fuel pressure signal whereby the established air-to-fuel ratio is maintained over a desired operating range of said internal combustion engine, the orifice in said orifice-venturi meter combination in said air inlet valve means being variable in size; and means coupled to said orifice and responsive to said air flow such that the air to fuel ratio is automatically changed for certain settings of said air inlet valve means. 
     
     
       10. The subject matter of claim 9 in which said pressure differential responsive means includes a cylinder having a double acting piston connected to said fuel valve for changing the setting of said fuel valve in one direction or the other in response to movement of said piston in said cylinder in one direction or the other; and an amplifier means including a slide valve having an inlet and first and second outlets, said inlet being connected to a source of vacuum and said outlets being connected respectively to opposite ends of said cylinder, movement of said slide valve from a center position increasing the vacuum applied to one outlet and decreasing the vacuum applied to the other outlet, said amplifier further including pressure responsive diaphragm means engaging said slide valve and having inlet passages on opposite sides connected respectively to receive said air pressure signal and fuel pressure signal whereby movement of the slide valve as a result of a differential pressure across said diaphragm means applies an amplified differential pressure across said double acting piston in said cylinder. 
     
     
       11. The subject matter of claim 10, including a vacuum accumulating chamber connected between the manifold of said internal combustion engine and the inlet of said slide valve to provide said source of vacuum. 
     
     
       12. The subject matter of claim 10, in which small bleeder holes are provided in the connection between said outlets and ends of said cylinder for said double acting piston to permit the proper fuel valve position to be maintained during rapid pressure changes as a result of rapid changes in inlet air flow.